This invention relates to an improved key and lock system whereby a single key is capable of operating two dissimilar lock mechanisms. The single key according to the invention has conventional handle and shank portions and is so designed such that a first set of notches and projections extending along one entire longitudinal edge of the key shank is used to operate a standard locking device, whereas a second set of notches and projections extending partially along the opposite longitudinal edge of the key shank on its outer extremity is used to operate a second smaller lock having a shorter barrel. The lock and key system according to the invention has particular applicability in multiple dwelling arrangements where a single key for the main exterior access door and for the mailbox unit affords a great convenience.
Normally, in a multiple dwelling apartment or condominium complex, each housing unit requires a standard size pin-tumbler lock mechanism for securing the main exterior door of the unit. In addition, each housing unit is provided with a mail receptable having a lock which is normally substantially smaller in size than the standard size exterior door lock. Moreover, the size of the internal tumblers for the mail receptacle and exterior door locks will differ substantially, and the relative number of tumblers in the locks may vary as well. The smaller size of the mail receptacle lock is necessitated by the physical size of the mailbox itself, while the number of internal tumblers is specified in the present U.S. Postal Services regulations, which requires that the lock be a 5 pin-tumbler type lock (see U.S. Postal Service, Regulations and Manufacturing Standards, Apartment House Mail Receptacles, Publication No. 17, July 1974, effective May 1, 1975).
As a result of the necessity to use substantially different locks, apartment dwellers and condominium owners have found it necessary to carry two separate keys to permit access to their apartments and mailboxes, which has been found to be in some cases a substantial inconvenience.
Various arrangements have been proposed in the past for operating more than one lock with a single key. The most well-known is the so-called "master key" device. In such a device, a lock is operable by either of two separate key configurations. A series of basically similar locks in size and tumbler number may be so designed and constructed that one of the key configurations is common to all of the locks (the master key arrangement), and the other configuration varies with each lock. A typical "master key" arrangement is shown in U.S. Pat. No. 2,039,126 to Svoboda.
Another arrangement permitting the use of one key in more than one lock configuration is disclosed in U.S. Pat. No. 1,438,336 to Schroeder. A flat key is provided with two sets of notches and projections along its two longitudinal edges. The first set of notches and projections actuates the tumblers in a first lock mechanism and thus renders the lock operable. When the key is inserted upside down into a second lock mechanism having a similar lock barrel, it actuates the tumblers in the second lock so as to render that lock operable as well.
Although the aforementioned devices disclose lock systems where one key operates two locks, in each case the two locks are substantially similar. In the master key arrangement, the portion of the lock which the master key operates is in fact identical in each lock. In the device shown in the Schroeder U.S. Pat. No. 1,438,336, each lock must have substantially the same barrel and thereby differ only in the setting (length) of the tumblers. Neither configuration permits the use of two substantially different size lock mechanisms with a single key.